The present invention relates to an apparatus for mixing and aerating a composting material, and particularly to an apparatus which is suitable for use with a relatively light composting material such as straw.
Composting is a well-known method for converting solid wastes into a useful commodity. Composting of municipal waste and certain agricultural wastes is currently practiced on a relatively large scale. Composting is being considered for disposal of additional agricultural wastes as environmental regulations render traditional disposal methods unacceptable. In certain seed crop industries, grass seed for example, it has long been the practice to harvest the seed and then burn the relatively large volume of grass straw remaining. The grass seed industry is now under pressure however to abandon large scale burning of grass straw due to its effect on air quality. Similar pressures are being exerted on other segments of the agricultural industry as well. As a result, composting is receiving increasing attention as an alternative to some of the traditional agricultural waste disposal methods.
Agricultural composting in general involves the partial decomposition of a solid material by the action of aerobic bacteria. When practiced on a small scale, it is relatively easy to maintain the aerobic conditions required by the bacteria; it is much more difficult to do on a larger scale. Failure to maintain aerobic conditions throughout the composting material results in anaerobic decay of the material, which in this situation is less efficient than aerobic decomposition, and normally emits objectionable odors. This combination of undesirable characteristics provides strong incentive to maintain aerobic composting conditions at all times.
There are known machines for physically mixing compost to maintain aerobic conditions. An example is U.S. Pat. No. 4,360,065 to Jenison et al. The Jenison cultivator comprises a horizontal rotating drum having a plurality of cultivator blades in two helical rows. As the drum is rotated, the blades travel edgewise through a pile of composting material to move the material sideways and pile it in a generally triangular pile. The '065 patent further describes other composting machines such as the Scarab, sold by Scarab Manufacturing and Leasing, Inc. of White Deer, Tex. U.S. Pat. No. 3,369,797 to Cobey describes a compost turner and windrow forming machine having a transversely mounted rotating drum for the turning of compost piles and the redepositing of the turned up material in a windrow. Yet another composting apparatus is described in U.S. Pat. No. 4,019,723 to Urbanczyk. The '723 patent describes a mobile composter for manure which moves a rotating drum over masses of inoculated manure to flail it, mix it, cool it and aerate it, while moistening the particles as the same time. After being conditioned and moisturized, the material is formed into a pile by a rear outlet opening. As with the Cobey composter, the flails mounted on the drum of the Urbanczyk machine travel edgewise through the composting material for flailing and mixing. U.S. Pat. No. 4,478,520 also to Cobey describes a compost turning machine which straddles a compost windrow while carrying a rotating drum for turning the composting material. The '520 composter additionally has an adjuster auger system outboard of the rotating drum to collect additional material and deposit it in the path of the rotating drum. This is the Cobey machine referred to earlier.
These known composters are useful and effective for composting materials having a relatively high density, and which may require the addition of moisture for maintaining the proper composting conditions. However, known composting machines have proved unsuitable for use in composting relatively light, tough composting materials such as grass straw. Applicant has discovered that the unsuitability of known composting machines is due in part to their inability to throw light stringy composting materials such as straw clear of the drum to prevent the straw from fouling the drum paddles.
An additional limitation of known composting machines resides in the difficulty of transporting them from one location to another. When used in an agricultural setting, this problem is particularly acute. It may be useful for instance, to compost agricultural waste in the field where the crop is grown. Where adjacent fields are separated by a fence transporting known composting machines between fields often requires driving the machines short distances on public roads, or loading the machines onto transporters to deliver them to the adjacent fields. Commercial scale composters are so wide that they cannot be driven through standard gates and fences between adjoining fields. If the composting machine must be transported to a location other than an adjacent field the problem is further aggravated because of the width of the composting machine; it is simply too wide to be driven on a public highway. It therefore must be loaded on a low-boy type trailer, and towed to the next location.
A need therefore exists for a composting machine which is suitable for use with relatively light agricultural waste products, or relatively light composting materials of any sort, and which is readily transportable between adjacent agricultural fields, or to a remote location.